Class: Fbp::Flow_node

Inherits:
Node
  • Object
show all
Defined in:
lib/fbp/flow-node.rb

Overview

Description

The flow node provides the ability of taking a network of Fbp nodes and wrap that network in a single node. This is done by creating a Flow description record. A Flow description record is a data structure that describes an entire network of Fbp noes. Given a Flow description record the Flow node class will create the entire network and then wrap that network so that writing to the input of a Flow node instance will forward that input to the first node in the created network. The output of the created network will be forwarded to the output of the Flow node instance.

There are module functions associated with the Flow node class. These functions provide the ability to take a Fbp network and create a Flow description record that describes the network. There are also functions that take a Flow description record and write them to the file system and read a file with a Flow description record and re-create the Flow description record.

Discussion

A Flow description record is an Array of Hashes with the following keys

Flow Description Record

[{:node => symbol_of_the_Fbp_node_class_name, :options =>{class_specific_hash}, :input => nil || [{index => output_channel_name_symbol}]}]

:node This is a symbol that is the name of the Fbp node to be instantiated.

:options This is a hash which is the IIP needed to parameterize the newly instantiated node.

:input This is either nil or an array of hashes. Each hash is keyed by the index in the array of nodes that are described by the Flow Description Record with the value being the symbol name of the output channel from which to get the input for the node.

Example Flow Description Record

The following is a simple network that will read in a file and split the file into two based upon a selector. The two outputs are sorted using the Sort Node and the output of the two different data streams and then writen out to different two files.

                             ======================================================
                             | {:selectors=>[{:data=>{:comparison=>Fbp::CONTAINS, |
==============               |      {:comparison=>Fbp::CONTAINS, :value=>"Magic", |
| ~/input.txt |===           |        :match=>:magic, :reject=>:output}}]         |
==============   |           ======================================================
                 | (IIP)                                   | (IIP)
                 \/                                        \/
==============================                    ======================
|                            |  output to input   |                    |
| Fbp::Test_file_reader_node |==================> | Fbp::Selector_node |
|                            |                    |                    |
==============================                    ======================
                                                    |     |
                    output to input                 |     |
=====================================================     |
|                     magic to input                      |
| =========================================================
| |
| |
| |
| |  =======================     ================================================================
| |  | {:sort_keys=>:data} |     | {:file_name=>"/Users/local/magic.txt", :file_open_mode=>"w"} |
| |  =======================     ================================================================
| |           | (IIP)                                  | (IIP)
| |           \/                                       \/
| |   ===================                  =============================
| ==> | "Fbp::Sort_node |=================>| Fbp::Text_file_writer_node |===> nil
|     ===================                  =============================
|
|     =======================    =================================================================
|     | {:sort_keys=>:data} |    | {:file_name=>"/Users/local/muggle.txt", :file_open_mode=>"w"} |
|     =======================    =================================================================
|              | (IIP)                                 | (IIP)
|              \/                                      \/
|     ===================                 ==============================
====> | "Fbp::Sort_node |================>| Fbp::Text_file_writer_node | ===> nil
      ===================                 ==============================

The beginning node in this network is the Fbp::Test_file_reader_node node. If that node is used to call The Fbp::make_flow_description function, the following will be returned.

[

:options=>{:file_name=>“/Users/local/input.txt”, :input=>nil},

:options=>{:selectors=>[{:data=>{:comparison=>6, :value=>“Magic”, :match=>:magic, :reject=>:output}]}, :input=>},

:options=>{:sort_keys=>:data, :input=>},

:options=>{:file_name=>“/Users/local/muggle.txt”, :file_open_mode=>“w”, :input=>},

:options=>{:sort_keys=>:data, :input=>},

:options=>{:file_name=>“/Users/local/magic.txt”, :file_open_mode=>“w”, :input=>}

]

There are some important things to note about this Flow Description Record. Each node is represented by a Hash. That hash has three items as noted previously. The order of the hashes in the array is important. It allows the :input key to be based upon the index of the node from which the referring node will receive its input.

For example the Fbp::Selector_node which is the second node in the array will receive its input from the Fbp::Test_file_reader_node node which is the first node in the array. This is denoted by the :input => [0=>:output] key value pair hash that defines the Fbp::Selector_node. This reads as The input of the Fbp::Selector_node comes form the node defined in the zeroth position of the Flow Description Record and takes its input from the output channel of that node

Future Development

Many FBP solutions have a visual configuration tool to form networks from existing nodes. The Flow node could be used in conjunction with a drawing tool to allow for non-programmer development of networks. This is an area that should be pursued.

Instance Attribute Summary

Attributes inherited from Node

#executing, #options, #output

Instance Method Summary collapse

Methods inherited from Node

#clean_option, #merge_options!, #set_option, #stop, #unregister_for_output_from_node, #write_to_output

Constructor Details

#initialize(flow_desc = nil) ⇒ Flow_node

When creating a new Flow_node instance one can optionally provide a flow description record.



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# File 'lib/fbp/flow-node.rb', line 244

def initialize(flow_desc = nil)
  super()
  @options[:flow_desc] = flow_desc
  @flow_created = false
  @node_objects = Array.new
end

Instance Method Details

#do_node_work(args) ⇒ Object

This will forward the do_node_work method to the first node in the network being serviced by this Flow_node instance.

Discussion

Should a way be provided to set which node in the network is the ‘first’ node?



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# File 'lib/fbp/flow-node.rb', line 322

def do_node_work(args)
  node =  @node_objects.first
  node.do_node_work(args) if !node.nil?
end

#execute ⇒ Object

This will forward the execute method to the first node in the network being serviced by this Flow_node instance.

Discussion

Should a way be provided to set which node in the network is the ‘first’ node?



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# File 'lib/fbp/flow-node.rb', line 308

def execute
  make_flow if !@flow_created
  node =  @node_objects.first
  node.execute if !node.nil?
end

#is_ready_to_run? ⇒ Boolean

Checks to see if this Flow_node instance has a flow description record. If the does have a flow description record then true will be returned otherwise false. A Flow_node instance will not execute until it has a low description record.



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# File 'lib/fbp/flow-node.rb', line 257

def is_ready_to_run?
      @options.has_key? :flow_desc
end

#register_for_output_from_node(node, output_channel = :output) ⇒ Object

This will forward the register request to the last node in the network being serviced by this Flow_node instance.

Discussion

Should a way be provided to set which node in the network is the ‘last’ node?



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# File 'lib/fbp/flow-node.rb', line 282

def register_for_output_from_node(node, output_channel = :output)
  last_name =  @node_objects.last
  last_name.register_for_output_from_node(node, output_channel) if !last_name.nil?  &&  node.nil?
end

#wait_until_completed ⇒ Object

This will forward the wait_until_completed method to the last node in the network being serviced by this Flow_node instance.

Discussion

Should a way be provided to set which node in the network is the ‘last’ node?



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# File 'lib/fbp/flow-node.rb', line 295

def wait_until_completed
 node =  @node_objects.last
 node.wait_until_completed if !node.nil?
end

#write_to_input(obj) ⇒ Object

This will write to the first object in the network being serviced by this Flow_node instance.

Discussion

Should a way be provided to set which node in the network is the ‘first’ node?



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# File 'lib/fbp/flow-node.rb', line 269

def write_to_input(obj)
  node =  @node_objects.first
  node.input_queue << obj if !node.nil? && !obj.nil?
end